Question 1

A microbiologist is trying to observe the detailed surface structure of a virus that is 20 nanometers in diameter. Which type of microscope should they use, and why?

Accepted Answer

A scanning electron microscope, because it provides detailed images of the surface of very small specimens.

Question 2

Which of the following best describes the difference between cationic and anionic stains in microbiology?

Accepted Answer

Cationic stains are attracted to negatively charged cell components, while anionic stains are repelled by them and stain the background.

Question 3

A student is using a microscope with a 10x ocular lens and a 40x objective lens. What is the total magnification?

Accepted Answer

$10 	imes 40 = 400$

Question 4

Which of the following statements about resolution in microscopy is correct?

Accepted Answer

Resolution is the ability to distinguish two points as separate and is improved by decreasing the wavelength of light.

Question 5

Why is immersion oil used with the 100x objective lens in light microscopy?

Accepted Answer

It reduces light refraction and increases resolution by matching the refractive index of glass.

Question 6

Which of the following is a correct example of binomial nomenclature?

Accepted Answer

Escherichia coli

Question 7

A Gram stain is performed on a sample from a human mouth. What result would you expect for the human epithelial cells?

Accepted Answer

They would appear Gram negative because they lack peptidoglycan and do not retain the crystal violet stain.

Question 8

Which of the following best describes the main difference between a simple stain and a differential stain?

Accepted Answer

A simple stain reveals cell shape and arrangement, while a differential stain distinguishes between different types of cells or structures.

Question 9

Which of the following is NOT a correct step in preparing a bacterial smear for staining?

Accepted Answer

Adding immersion oil before staining.

Question 10

What is the primary purpose of a mordant in a differential staining procedure?

Accepted Answer

To increase the binding of the primary stain to the target structure.

Question 11

Which of the following statements about the three domains of life is correct?

Accepted Answer

Eukarya includes fungi, plants, and animals.

Question 12

A researcher wants to identify an unknown bacterial species using a dichotomous key. What is the main feature of a dichotomous key?

Accepted Answer

It uses a series of paired, mutually exclusive choices to narrow down the identity of an organism.

Question 13

Which of the following would be the best method to visualize the internal structures of a bacterial cell?

Accepted Answer

Transmission electron microscopy

Question 14

Which of the following is a correct statement about modern taxonomy compared to Linnaeus’s system?

Accepted Answer

Modern taxonomy incorporates genetic and molecular data, while Linnaeus’s system was based on observable traits.

Question 15

Which of the following would be the most appropriate staining technique to identify the presence of endospores in a bacterial sample?

Accepted Answer

Endospore stain

Question 16

A sample is stained using a differential stain and shows both red and purple cells under the microscope. What does this indicate?

Accepted Answer

The sample contains both Gram-positive and Gram-negative bacteria.

Question 17

Which of the following would improve the resolution of a light microscope?

Accepted Answer

Using immersion oil to reduce refraction.

Question 18

Which of the following is an example of when a wet mount would be preferred over a stained preparation?

Accepted Answer

When observing the motility of live protozoa.

Question 19

Which of the following is true regarding the preparation of specimens for transmission electron microscopy (TEM) compared to scanning electron microscopy (SEM)?

Accepted Answer

TEM specimens are sliced into thin sections, while SEM specimens are coated with a thin layer of metal.

Question 20

Which of the following statements about the domains of life is correct?

Accepted Answer

Bacteria and Archaea both contain prokaryotic cells.

Microscopy, Staining, and Classification: Chapter 4 Study Guide

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